1. Field of the Invention
The present invention is related generally to the field of optical detection, and more particularly, to the field of optical detection and identification of additive taggants.
2. Description of the Related Art
Existing taggants are used by both private companies and individuals and the government in order to identify and authenticate numerous articles, such as financial documents (e.g., checks, stamps, vouchers, stock certificates, bonds, currency, passports, and the like). Further, attempts have been made by the government to use existing taggants to identify and track munitions, (e.g., bombs, and to perform bomb damage assessment (“BDA”). Although the identification of bombs prior to detonation is preferable, it is also important to detect and track the plume of a bomb, especially one containing biological warfare agents. Current taggants for BDA are made from rare-earth or organic materials. Unfortunately, it is necessary to add significant quantities to the explosive mixture of the bomb in order to be detected with stand-off sensors and the current taggants are prone to degradation during the explosion. Further, the existing taggants also have indiscriminate absorption spectra and are often difficult to detect above a background of spectral noise.
Taggants have also been used to test the safety and track the location of munitions, such as sporting firearms, ammunitions, and smokeless propellant powders. The types of taggants used are microscopic and sometimes magnetic particles that are mixed with explosives, and remain behind after the explosion, e.g., the firearm is discharged, takes place. Although invisible to the naked eye, under magnification these types of taggants are actually color coded pieces of a polymer material, e.g., plastic, that are meant to identify a particular batch of explosive powder. By tagging munitions when they are manufactured, it is possible to identify and return to this source in cases where the munitions were used in an illegal capacity, e.g., acts of terrorism, etc. Unfortunately, some studies have shown that the taggants used had an adverse effect on the propellant and explosive materials used in the munitions, thus causing the effectiveness and accuracy of the munitions to be reduced. This is due in some cases to the large quantities of taggant materials that were necessary in order to be detected post-discharge and other cases because of chemical interactions between the materials.
Prior art taggants have also been used in scenarios where it is necessary to differentiate between a friend or a foe in military or police situations. Referred to as “identification friend or foe” or IFF, this process uses an encrypted signal sent via radio frequency (RF) in order to identify friendly assets and resources and reduce fratricide. The signal is sent by an ‘interrogator’ and the reply is sent by a ‘transponder’. These coded signals are changed at a given interval and require extensive supporting hardware.
Additionally, attempts have been made to use taggants in various other identification and/or detection scenarios, such as for identifying counterfeit or pirated goods. In addition to frequently pirated goods such as software, currency and credit cards, compact discs and videotapes, clothing, and aircraft parts, goods such as food products, beverages, pharmaceuticals, perfumes, and the like are also affected. And this list is not exhaustive. Nearly all consumer brand products, specialty chemicals, currency, or industrial products are susceptible to counterfeiting or tampering. In fact, according to the ICC Counterfeiting Intelligence Bureau, counterfeit products account for 5% of world trade, representing about US$250 billion annually. Taggants are useful as product markers to confirm authenticity.
Available technology for product identification includes, for example, bar codes, which are large, susceptible to wear and tear, require line-of sight reading, and usually identify categories of products as opposed to acting as unique identifiers. Another technology, Radio-frequency identification tags (RFIDs), do offer unique identifiers (unlike barcode tags), but as yet are no smaller than 1 mm by 0.5 mm and contain multiple breakable parts, such as a microchip and an antenna. This size is prohibitive for many applications. Further, the RF bands are subject to cross-talk and other interference and are not conducive to detection from too great a distance.
Still another taggant technology includes printing fluorescent marks on an item, such as a heat-sealable label, to generate a unique identification number or indicia. The unique identification number or indicia is then read by a reader system that includes an illumination source that excites the fluorescent marks in combination with a color sensitive device, such as a camera, which is “blind” to the illumination wavelength but which can discern the fluorescence color and a relative spatial order of the fluorescent marks. Such labels are limited in their application and are susceptible to wear and tear. Such labels cannot be used for BDA or other harsh environmental or long-range detection applications.
Yet another marking technology includes melamine alkyd polymer particles, which range in sizes from approximately 5-45 μm. The material is layered in various thicknesses to ascertain a code by way of 4 to 10 layers of variable coloration. The codes are read using a microscope with approximately 40 times magnification or automatic reading devices. This microscopic layering technology is susceptible to degradation and due to size limitations and reading requirements, is not suitable for many taggant situations described herein.
Finally, biological taggants have been used which are based on bio-engineered, recognition molecules used to detect and measure safe, inert markers, which have been added to products as an internal “fingerprint”. In order to test for the presence of the taggant, it is necessary to either physically access the product for a real-time dipstick test or to conduct quantitative field and laboratory tests. These taggants are limited to use with certain petroleum, chemicals, pesticides, printing, food and beverages and require invasive testing to determine the presence thereof.